This invention concerns tapping devices for forming threads in workpieces. Tapping is often necessary in manufacturing, and there have previously been developed in die tapping units to carry out tapping when the part is also been formed. It has long been the practice to operate such tapping units with the die press motion, as described for example in U.S. Pat. No. 5,173,015, and in U.S. patent application Publication No. 2002/0102142 and U.S. Pat. No. 6,547,496 issued from the parent application of the present application.
An in-die tapping unit which is operated by the press motion has certain disadvantages caused by the fact that presses are usually crank driven with a sinusoidal velocity. Since a tap has a maximum speed at which it can be used, and this cannot be greater than the peak press velocity, tapping is carried out for most of the cycle more slowly than would otherwise be possible. Also, the timing of the tapping is tied to the press motion, limiting flexibility in designing the process.
It has thus been proposed to use an electric servo motor to drive in die tapping unit to maximize the speed with which the tapping can be completed. Other advantages are the ease of tapping in various directions, and of executing tapping at any time during the press cycle.
Changing taps must be done frequently due to limited tap life, and when using a servo motor tap drive, changing taps has often required substantial down time due to the need to disassemble or remove the complete tapping units from the press in order to change a tap.
This problem is further exacerbated by the need to change pitch adapters having mating threads which control the rate of advance of the tap during tapping. These adapters must also be changed when changing tap sizes, and often this requires removal of the entire unit and disassembly in order to replace the pitch adapter.
It is the object of the present invention to provide an electro servo motor driven in die tapping unit which allows quick and easy replacement of taps and pitch adapters without the need to disassemble or remove the entire tapping unit.